are these good rules?

First of all, the mini-fig must roll a skill roll to begin the process.
If the mini-fig rolls a 6 (or higher) the missile or grenade hits dead on like Bonn-o-Tron.
If he rolls lower, subtract the roll from 6 and thats how many inches away the missile or grenade hits.
To figure what it hits away from original target, roll a Directional dye(see my avatar).